The human granulocyte colony stimulating factor (hG-CSF) is a kind of polypeptide which is essential in the formation of various blood cells as a result of proliferation and differentiation of hematopoietic stem cells. Its major effect is to promote the increase in number of granulocytes, in particular neutrophils. Neutrophils play an important part in the protection of the living body from infection.
However, their life spans are short and, therefore, constant supplementation is required by proliferation and differentiation of precursor cells. The therapies widely employed in recent years for proliferative tumors simultaneously inhibit the growth of neutrophil precursors, hence cause a severe side effect, namely a reduction in neutrophilic protection in cancer-bearing patients making them more susceptible to infection. hG-CSF is expected to be effective in alleviating this undesirable side effect through promotion of the increase in the number of neutrophils on one hand and, on the other, in preventing and treating infectious diseases. Furthermore, hG-CSF is active in causing differentiation of leukemic cell lines in vitro and therefore may possibly be useful as a therapeutic agent for leukemia. The hG-CSF polypeptide derivatives according to the invention are superior in hG-CSF activity to the known hG-CSF and are expected to be useful as drugs.
With the recent rapid progress in recombinant DNA technology, genes for proteins involved in the proliferation and differentiation of blood cells have been isolated in succession. Such factors are in production by genetic engineering techniques using microorganisms or animal cells.
A cDNA for hG-CSF was isolated from the human squamous cell carcinoma cell line CHU-II, its base sequence determined and its expression in COS cells reported by Nagata et al. [Nagata et al.: Nature, 319, 415 (1986)]. Souza et al. also isolated a cDNA from the human bladder cancer cell line 5637, determined its base sequence and reported its expression in Escherichia coli (E. coli) [Souza et al.: Science, 232, 61 (1986)].
The amino acid sequence of the protein encoded by the above two cDNAs is in agreement with the amino acid sequence (Table 1) of the protein encoded by the cDNA isolated from normal human peripheral blood macrophages by the present inventors.
TABLE 1 __________________________________________________________________________ ##STR1## ##STR2## ##STR3## ##STR4## ##STR5## ##STR6## ##STR7## ##STR8## ##STR9## ##STR10## __________________________________________________________________________ (X = H or Met)